The present invention relates to a novel vehicle lamp and more particularly to the art of forming a portion that requires heat-resistance less costly in a good external appearance.
Many component parts of vehicle lamps, for example, automotive lamps are formed of resin material and some component parts require heat-resistance. For example, quite a high temperature is present in the vicinity of a light source portion such as a light source bulb, so that the component part used in the vicinity of the light source portion requires heat-resistance.
In case that material having poor heat-resistance is used for the portion that requires heat-resistance as in the vicinity of the light source portion, a problem of thermal deterioration occurs.
Even though highly heat-resistant resin material is used as the material for some component part to be used in a portion that requires heat-resistance, the problem is that the vehicle lamp tends to become costly because resin material having great heat-resistance is expensive.
Moreover, highly heat-resistant resin material is poor in process ability and difficult to take out a fine detail and to planish. The surfaces of component parts for use in the vehicle lamp are often subjected to vapor deposition. Even though the deposition is applied to the surface, no fine deposited plane is obtained after the deposition unless the surface is planished. Therefore, an under coating layer is given to the surface where the deposition is performed to make the surface a smooth plane and then the deposition is applied onto the under coating layer. Consequently, the process step of forming the under coating layer is required and material for the under coating layer becomes additionally needed, which also causes an increase in the cost of the vehicle lamp. Further, highly heat-resistant resin material is poor in fluidity and this results in increasing the thickness, so that not only the weight of the component part but also the material cost is increased further.
Meanwhile, JP-U-60-094705 describes the art of forming highly heat-resistant resin material by monolithic molding in the portion located right above a light source bulb as a light source out of a lamp body.
In the art indicated in JP-U-60-094705, highly heat-resistant resin material is used for only part of the component part (lamp body) and the advantage is that the amount of the expensive heat-resistant resin material used is reducible.
According to the art described in JP-U-60-094705, the portion formed of the heat-resistant resin material is located on the surface of the lamp body. Therefore, the surface of the portion formed of the heat-resistant resin material becomes poor in formability, whereupon the formation of an under coating layer becomes essential in performing vapor deposition.
As the surface of the portion formed of the heat-resistant resin material is exposed to the outside, a seam line is produced between the portion formed of the heat-resistant resin material and the portion formed of resin material other than the heat-resistant resin material; the problem is that the external appearance is spoiled. When such a line is produced once, it stands out on the deposited plane even when the deposition is applied thereto and the external appearance is never improved.